Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Process for Preparing CCR-5 Receptor Antagonists
Utilizing 4-substituted 1-Cyclopropane-sulfonyl-Piperidinyl Compounds
Field of the Invention
This application discloses a novel process for the synthesis of the CCR5
receptor antagonist 4-[4-[(R)-[1-[cyclopropylsulfonyl)-4-piperidinyl](3-
fluorophenyl)methyl]-3(S)-methyl-l-piperazinyl]-1-[(4,6-dimethyl-5-
pyrimidinyl)carbonyl]-4-methylpiperidine.
Background of the Invention
4-[4-[(R)-[1-[cyclopropylsulfonyl)-4-piperidinyl](3-fluorophenyl)methyl]-3(S)-
methyl-1-piperazinyl]-1-[(4,6-dimethyl-5-pyrimidinyl)carbonyl]-4-
methylpiperidine],
the compound of Formula Id having the structure shown below:
F \
CH3
CHg
4~k N
1.11 N N H3C N
O N / I I
0 CH3 Formula Id
The compound of Formula I is an antagonist of the CCR5 receptor and is useful
for the treatment of AIDS and related HIV infections. CCR5 receptors have also
been reported to mediate cell transfer in inflammatory diseases such as
arthritis,
rheumatoid arthritis, atopic dermatitis, psoriasis, asthma and allergies, and
inhibitors of such receptors are expected to be useful in the treatment of
such
diseases, and in the treatment of other inflammatory diseases or conditions
such
as inflammatory bowel disease, multiple sclerosis, solid organ transplant
rejection
and graft v. host disease. This compound is described and claimed in Example
1 BF of United States Patent No. 6,720,325, (the '325 patent), the entire
disclosure of which is incorporated herein by reference. The '325 patent
describes a synthesis of the compound of Formula Id utilizing a step-wise
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synthetic scheme which builds up a 4-aidehyde-substituted piperidine "left
half'
intermediate to the compound of Formula Id and a 4-substituted piperazine
r'right
half' intermediate of the compound of Formula Id. The left and right half
intermediates are joined in a subsequent amidation reaction in the presence of
benzotriazole, providing an intermediate which undergoes further
derivatization
reactions to form the compound of Formula Id. An improved synthesis scheme
for preparing the compound of Formula Id is described in Published
Intemational
Application No. WO 2006/074270 (the '270 publication), and is illustrated
below
in Scheme I.
SCHEMEI
H
SO,,Ne
PMB'N
IVa
NeHSO, NaOH
NChz
^~COOEt enbeldehyde COOEt R~N CHO q
HNr J7 NaBH(OAe), PMB' INJI Pyrrelldine PMB'NrJT benzoUlezole KOt-Bu P \
~ /
11 III IV
MgBr
H, TFAAIEt~1 I~ HNaOH I~
PMB'N -Cbz F'cyN~ k,.,N, Cbz H'N, ON, Clu
O
v Va N
CbzOSu
1. NeOH
2. (COOHh F_0
Nl ~ (COOHh
PMB' vNN
W
~ I i
O O 1.50%MaOH ,
~ N,J 2. HBr ~x f T N ~ 2 HBr
Et,N N ~N`
NH
O O O O
VII Vlll
t~
\
MeMpCI
O CH' I N~ CCrt~~ N~
H~N ~O vN~sC` ~~~1 AIMs, ON~N~CCYy1~"1,
n 1 1N N J` N
I% O CH, IA 1'IOCHo
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The synthetic method described in the '270 publication utilizes
intermediate compound V, which has two amine groups protected, respectively,
by PMB and CBZ protecting groups. The synthetic method utilizes the reactivity
differences of the two protecting groups to enable further substitution of the
intermediate, providing the compound of Formula Id. The disclosure of the '270
publication is incorporated by reference herein in its entirety. The above-
described synthetic processes utilize numerous steps to provide the desired
CCR5 receptor antagonist compound. Each of the processes described above
processes proceed through intermediates having poor handling characteristics,
making scale up of the processes to commercial scale problematic. Some of the
steps in the above-described processes are characterized by poor yields,
making
cost effective production of the desired receptor antagonist problematic. In
some
processes, additional purification steps are required, for example,
precipitating
and purifying a bisulfite adduct of the compound, which further reduces the
efficiency of the process from the standpoint of material utilization and
processing
time.
Obiectives
In view of the foregoing, what is needed is a synthetic scheme useful for
preparing the CCR5 inhibitor compound of Formula Id which requires fewer
steps, utilizes safer and/or more tractable materials and provides a reaction
scheme affording practical scale up to a batch size suitable for commercial
scale
preparation. These and other objectives and/or advantages are provided by the
present invention.
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Summary of the Invention
In one embodiment, the present invention is a process for preparing the
compound of Formula I,
F ~
CH3
N Rio
'-i - NI ~r N H C
s N
OSO N
tN 0 CH3 Formula I
the process comprising:
(a) synthesizing the compound A4
F O
N
0
% C N ~NH
2HBr
A4
by reacting the compound A3
Y
OH
\S/N
v \O
A3
wherein "Y" is selected from: (i) -CN; (ii) -O-S(O)2R4, wherein R4 is
selected from alkyl and aryl; (iii) a halogen;
N ~
NN
(iv) triazole N-N [N] , and benzotriazole
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successively with: (1) 3-methylpiperidine-l-carboxylic acid benzyl ester; (2)
3-
fluorophenyl magnesium bromide; and (3) HBr, in accordance with scheme 1 c
Scheme 1 c
Y OH F \
H~'~, U
caz =
N 2 F MgBr N
0-S-0 % \ N . NH
3. HBr \
0 2HBr
A3 A4
(b) coupling the free base form of intermediate compound A4 formed in
Step "a" with the compound of Formula DI
H3 :~,-NI
N ~ N
0 CH3 Formula Dl
in the presence of a reactant having the form "E-G", thereby forming the
compound of Formula IX,
H,
N
,N H, yN`
O~ 1
O \ N
0 cH, Formula IX
wherein, for the "E-G" reagent, "G" is selected from: (i) CN; (ii) a sulfonate
ester of the Formula [-OS(O)2-R'], wherein R' is selected from an alkyl or
aryl group; (iii) halogen; (iv) -C(O)-O-CX3, wherein "X" is a halogen; and
(iv) benzotriazolyl, and wherein "E" is an electrophile capable of
scavenging the oxygen of the ketone carbonyl group of the compound of
Formula Dl upon nucleophilic attack at the corresponding carbonyl
carbon; and
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(c) reacting the compound of formula IX in a suitable solvent with an
organometallic reagent supplying an R10 moiety, where R'0 is selected
from an aliphatic and an aromatic moiety, followed by a workup to yield
the compound of Formula I.
In some embodiments, preferably the compound of Formula A3 is a
compound of Formula A3'
N iro N
O N ~ ~
D--II-N
OH
A3'
In some embodiments, preferably the organometallic reagent used in Step
"c" is selected from an organometallic reagent supplying an R10 moiety
selected
from alkyl, for example, methyl, aryl, alkaryl, for example, benzyl, alkenyl,
for
example, allyl, allenyl and alkynyl, for example, propargyl. In some
embodiments it is preferred to select the organometallic reagent supplying the
R10 moiety from magenesium, lithium, zinc, and tin organometallic reagents,
more preferably, the organometallic reagent is a magenesium organometallic
reagent, more preferably, alkyl Grignard reagents. In some embodiments it is
preferred to use methyl Grignard as the organometallic reagent in Step "c",
thus
"R1 " in the compound of Formula I is (methyl-).
In some embodiments it is preferred to select the compound E-G from
cyanating agents, for example, HCN, acetone cyanohydrin; cyclohexanone
cyanohydrin; a mixture of (C2H5)2AICN and Ti(OPr)4; a mixture of acetic acid,
and H2SO4 with NaHSO4, KHSO3 or Na2S2O5 and a cyanide source such as
NaCN or KCN; trimethylsilylcyanide; glycolonitrile; mandeloilitrile;
glycinonitrile;
acetone amino nitrile; and dimethylaminoacetonitrile. More preferably, the E-G
compound is acetone cyanohydrin.
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In some embodiments, it is preferred to provide the compound of Formula
A3 by the process comprising:
(a) converting a sulfonamide of Formula Al
A
O N
S/
\ / \O
Formula Al
wherein substituent "A" is selected from: (i) a substituent of the Formula -
C(O)-X, wherein "X" is selected from: halogen; trialkylsilane; NR2R3,
wherein R2 is independently selected from hydrogen, an aliphatic moiety,
an aromatic moiety, and a heterocyclic moiety, and R3 is independently
selected from hydrogen, O-R2, NR22, an aliphatic moiety, an aromatic
moiety, and a heterocyclic moiety, or R2 and R3 taken together form a ring;
and -S-R1 and -O-R', wherein R' is selected from hydrogen, an aliphatic
moiety, including an alkyl, alkyaryl, an aromatic moiety, and a heterocyclic
moiety; (ii) an alkyl-alkenyl-substituent of the formula -CHC(R20)2 wherein
R20 is independently selected from H, alkyl and aryl; (iii) -CN; and (iv)
-CH2OH,
to an aldehyde compound of the Formula A2b,
O
>4LNGJII
0 Formula A2b, and;
(b) reacting the aldehyde of Foi-mula A2b with benzotriazole to form the
benzotriazole-adduct of Formula A3.
In some embodiments, for example when substituent "A" in the compound
of Formula Al is CN, or contains a carbonyl carbon, for example: when "A" is
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C(O)-X, wherein "X" is halogen and -O-R', wherein R' is selected from hydrogen
and an aliphatic, aromatic, and a heterocyclic moiety; and when "A" a
substituent
of the Formula -C(O)NR2R3, where R2 and R3 is defined above, it is preferred
to
use reducing conditions to prepare the aidehyde intermediates, for example,
treatment with diisobutyl aluminum hydride (DibAIH) followed by an aqueous
workup. In some embodiments, for example, when "A" in the compound of
Formula Al is an alcohol, for example CH2-OH, it is preferred to use oxidizing
conditions to prepare aidehyde intermediate. Examples of oxidizing conditions
include treatment with enzymatic alcohol dehydrogenase, Dess-Martin periodate,
Swem Oxidation, Moffat Oxidation, inorganic catalyst mediated oxidation, for
example, oxidation using N-methylmorpholine oxide mediated by RuC13, and
organic catalyst mediated oxidation, for example oxidation with sodium
hypochlorite catalyzed by 2,2,6,6-tetramethyl-1-piperinyloxy (TEMPO).
In some embodiments wherein "A" is selected to be an alkyl-alkenyl-
moiety, it is preferred to carry out oxidation with ozone followed by a
suitable
workup. Examples of suitable workup include reductive workup using
dimethylsulfide, and dihydroxylation followed by diol cleavage.
In some embodiments, it is preferred to provide the compound of Formula
Al from the compound of Formula A1 c in accordance with Scheme IIA
Scheme IIA
0
S/CI
A \ / \O A
HN O SN
Alc ~ % Al
wherein substituent "A" is selected from: (i) a substituent of the Formula -
C(O)-X,
wherein "X" is selected from: halogen; trialkylsilane; NR2R3, wherein R2 is
independently selected from hydrogen, an aliphatic moiety, an aromatic moiety,
and a heterocyclic moiety, and R3 is independently selected from hydrogen, 0=
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R2, NR22, an aliphatic moiety, an aromatic moiety, and a heterocyclic moiety,
or
R2 and R3 taken together form a ring; and -S-R1 and -O-R', wherein R, is
selected from hydrogen, an aliphatic moiety, including an alkyl, alkyaryl, an
aromatic moiety, and a heterocyclic moiety; (ii) an alkyl-alkenyl-substituent
of the
formula -CHC(R20)2 wherein R20 is independently selected from H, alkyl and
aryl;
(iii) -CN; and (iv) -CH2OH.
In some embodiments it is preferred to select the compound of Formula
Al to be the nitrile-substituted compound of Formula A2a and convert it to an
aidehyde by reaction with diisobutyl aluminum hydride (DIBAL-H), followed by
an
acid workup and prepare in sitU therefrom the corresponding benzotriazole-
adduct of Formula A3 in accordance with Scheme 1 B1
Scheme 1 B1
1. DIBAIH q ~\
Aueous tric >1:: Ad wop \ N-N A3
N
In some embodiments it is preferred to provide the compound of Formula
A2a by dehydrating the corresponding sulfonamide-4-amide compound of
Formula Al a, for example, by treatment with phosphorous oxychloride in
accordance with Scheme 1 B2.
Scheme 1 B2
~O-N O POCl3 O-N CN
II C:X ~ II
O NHZ O
Ala A2a
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In some embodiments it is preferred to provide intermediate compound A3
in accordance with Scheme IIB,
Scheme IIB
Step I
cil,,_,l-'-~soZa 0
0
TEA C~ NHZ
NHZ
N
NH ~1"*O
2Ba 0 2Bb
Step2
CI ~CN
Path A /S;\
POC13 / ~Bc
2Bb H3C-CN
Path B 0
Potassium ~\N`/ `NH
t-butoxide/THF O O 2
2Bd
Step 3
2Bc K- t-butoxide/
THF CN
S / N
~ \0
P~C13
2Bd H3C-CN A2a
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Step 4
CN
1. DIBALH N
~
6 2. Aqueous Citric N
Acid workup
N OH
I 3. H% O
0=S=0 N- N ~S/ N
f ~ 'N `O A3
A2a -
synthesis scheme IIB comprising:
(i) reacting isonipecotamide (compound 2Ba) with 3-chloropropane-sulfonyl
chloride to form the adduct compound 2Bb;
(ii) following Path A to convert the amide substituent of compound 2Bb to a
nitrile adduct, thereby forming compound 2Bc or altematively following
Path B, cyclizing the chloropropyl moiety of the sulfonamide substituent to
form compound 2Bd;
(iii) When Path A was followed in Step 2, cyclizing the 3-chloropropyl
substituent on the sulfonamide substituent of compound 2Bc to form
compound A2a, and when Path B was followed in Step 2, converting the
amide substituent of compound Bd to a nitrile substituent; and
(iv) reacting compound A2a sequentially with: (1) diisobutyl aluminum hydride
(DibAIH) to reduce the cyano substituent to the corresponding aldehyde;
(2) aqueous citric acid; and (3) benzotriazole to form benzotriazole adduct
compound A3.
In some embodiments of Scheme IIB it is preferred to utilize acetonitrile
(ACN) as a-solvent and triethylamine (TEA) as a base in the formation of the
sulfonamide in Step 1. In some embodiments utilizing Scheme IIB, it is
preferred
to perform conversion of the amide substituent in the compound of Formula 2Bd
or 2Bb to a nitrile substituent by treating compound 2Bb or 2Bd with
phosphorous
oxychloride in acetonitrile. In some embodiments it is preferred to perform
the
nitrile conversion utilizing other dehydrating agents, for example, thionyl
chloride,
phosgene, phosphorous pentoxide, and oxalyl chloride. In some embodiments
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using altemative dehydrating agents to perform this transformation,
conditions,
for example, those described in Comprehensive Organic transformations, 2"d
ed.,
R.C. Larock, Wiley-VCH, NY 1999, on pages 1983 to 1985, which are
incorporated herein by reference, are employed. In some embodiments utilizing
Scheme lib, it is preferred to carry out the cyclization to form the
cyclopropane
substituent by treating compound 2Bc with potassium tert-butoxide in
tetrahydrofuran (THF) solvent.
In some embodiments it is preferred to carry out an altemative form of
Scheme IIB, following in Step 2, pathway B.
In some embodiments it is preferred to prepare the compound of Formula
Id,
F ~
CH3
C
H3
N~rN
~N H3C N
S
~O / 11
N N
0 CH3 Formula Id
by a process comprising:
(i) reacting isonipecotamide with 3-chloropropane-sulfonyl
chloride to form the adduct compound 2Bb,
0
CI NH2
= N
1[~o
0 2Bb
(ii) converting the amide substituent of compound 2Bb to a
nitrile, thereby forming compound 2Bc,
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CN
CI
/N
11"~'O
0 2Bc
(iii) cyclizing the 3-chloropropyl substituent on the sulfonamide
substituent of compound 2Bc to form compound A2a,
CN
O S/ N
`O
A2a
(iv) converting compound A2a to the corresponding aldehyde by
reduction of the nitrile substituent with DIBAL-H followed by
an acid workup and subsequently reacting the aldehyde in
situ with benzotriazole to form benzotriazole adduct
compound of Formula A3,
N N I ~
N
OH
0 SN
~O A3
(v) synthesizing the compound A4,
F O
N
~g.-N NH
= ~./
17- 0 2HBr Formula A4,
by reacting the compound A3
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N
N I \
N ~ /
OH
~
O
A3
successively with: (i) 3-(S)-methylpiperazine-l-carboxylic acid
benzylester; (ii) 3-fluorophenyl magnesium bromide; and (iii) HBr;
(vi) liberatihg the free base of compound A4 from the hydrobromide salt
prepared in Step "v";
(vii) reacting the free base liberated in Step "vi" with the compound of
Formula Dl,
H3 NI
01'~(
N ~ 0 CH3 Formula Dl,
in the presence of a moiety of the Formula "E-G", where "E" is an
electrophile capable of scavenging the oxygen of the ketone
carbonyl group of the compound of Formula Dl upon nucleophilic
attack at the corresponding carbonyl carbon and "G" is a leaving
group selected from the group consisting of CN, halogen, -OS02-R'
(wherein R' is selected from an alkyl or aryl group), -C(O)OCX3
(wherein "X" is a halogen), and benzotriazolyl, to form the compound
of Formula IX,
CH3
N
N N Hg N
O-K-0 N N
H3 Formula IX,
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wherein "G" is as defined above for the E-G reagent selected; and
(viii) reacting the compound of Formula IX with a methyl Grignard reagent
to yield the compound of Formula Id.
In some embodiments the present invention provides the following
compounds:
OH
A T A
\ N\ N 0\ N
O O
S
d~b db
and
OH
T
03
\ ,N
Rz,.,/~/ Sb
wherein, "A" is as defined above, T is selected from: (i) CN; (ii) a sulfonate
ester of the Formula [-OS(O)2-R"], wherein R" is selected from an alkyl or
aryl
group; (iii) halogen; (iv) -C(O)-O-CX3, wherein "X" is a halogen; (v)
triazole; and
(vi) benzotriazole, and Rz is selected from: a halogen and or O-R13 where R13
is
selected from -C(O)R14, -C(O)OR14, or S(O)2R14, where R14 is H, an aliphatic
moiety and an aromatic moiety.
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Detailed Description of the Invention
As mentioned above, and described in published international application
no. 2006/074270, the compound of Formula Id is a CCR5 receptor antagonist
and is useful in the treatment of AIDS and related HIV infections and may be
useful in the treatment of other diseases, for example, inflammatory diseases.
Except where stated otherwise, the following definitions apply throughout the
present specification and claims. These definitions apply regardless of
whether
a term is used by itself or in combination with other terms.
"Acyl" means an H-C(O)-, alkyl-C(O)-, cycloalkyl-C(O)-, or aryl-C(O)- and
the like. The bond to the parent moiety is through the carbonyl.
"Alkyl" means an aliphatic hydrocarbon group which may be straight or
branched and comprising about 1 to about 20 carbon atoms in the chain.
Preferred alkyl groups contain about 1 to about 12 carbon atoms in the chain.
More preferred alkyl groups contain about 1 to about 6 carbon atoms in the
chain. Branched means that one or more lower alkyl groups such as methyl,
ethyl or propyl, are attached to a linear alkyl chain. "Lower alkyl" means a
group
having about 1 to about 6 carbon atoms in the chain which may be straight or
branched. The term "substituted alkyl" means that one or more hydrogen atoms
on an alkyl group may be substituted by one or more substituents which may be
the same or different, each substituent being independently selected from the
group consisting of halo, alkyl, aryl, cycloalkyl, cyano, hydroxy, alkoxy,
alkylthio,
amino, -NH(alkyl), -NH(cycloalkyl), -N(alkyl)2, carboxy and -C(O)O-alkyl. Non-
limiting examples of suitable alkyl groups include methyl, ethyl, n-propyl,
isopropyl and t-butyl.
"alkyl-alkenyl-" means one or more aliphatic hydrocarbon groups of from
about 1 to about 20 carbon atoms bonded, to a double bonded hydrocarbon
moiety, for example, -(H)C=C(R2), wherein R is selected independently for each
occurrence from any of the substituents herein mentioned.
"Alkylsulfonate" means an alkyl-S(02)-O- group in which the alkyl group is
as previously described. Preferred groups are those in which the alkyl group
is
lower alkyl. The bond to the parent moiety is through the oxygen.
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"Aryl" means an aromatic monocyclic or multicyclic ring system
comprising about 6 to about 14 carbon atoms, preferably about 6 to about 10
carbon atoms. The aryl group can be optionally substituted with one or more
"ring system substituents" which may be the same or different, and are as
defined herein. Non-limiting examples of suitable aryl groups include phenyl
and
naphthyl.
"Cbz" means carbobenzyloxy.
"Cycloalkyl" means a non-aromatic mono- or multicyclic ring system
comprising about 3 to about 10 carbon atoms, preferably about 5 to about 10
carbon atoms. Preferred cycloalkyl rings contain about 5 to about 7 ring
atoms.
The terms "Halide", "Halo" and "Halogen" mean fluoro, chloro, bromo or
iodo moieties.
The terms "Heterocycyl" and "Heterocyclic" refer to a non-aromatic
saturated monocyclic or multicyclic ring system comprising about 3 to about 10
ring atoms, preferably about 4 to about 7 ring atoms, in which one or more of
the
atoms in the ring system is an element other than carbon, for example,
nitrogen,
oxygen or sulfur, alone or in combination, with the proviso that no adjacent
oxygen and/or sulfur atoms are present in the ring system. Preferred
heterocyclyl
groups contain about 5 to about 6 ring atoms. The prefix aza, oxa or thia
before
the heterocyclyl root name means that at least a nitrogen, oxygen or sulfur
atom
respectively is present as a ring atom. Any -NH in a heterocyclyl ring may
exist
in a protected form, for example, an -N(Boc), -N(cbz), -N(Tos) group. Such
protections are also considered part of this invention.
The term "heterocyclic" as used herein, also includes heteroaryl, which,
as used herein, is a mono- , bicyclo, or polycyclic, chemically feasible ring
system containing one or more aromatic rings having in at least one aromatic
ring at least 1, up to about 4 nitrogen, oxygen or sulfur atoms. Typically, a
heteroaryl group represents a cyclic group of five or six atoms,'or a bicyclic
group of nine or ten atoms, or a polyfused ring system with each ring
containing
from about 4 to about 6 atoms, at least one of which is,carbon, and having at
least one oxygen, sulfur or nitrogen atom interrupting a carbocyclic ring
having a
sufficient number of pi (n) electrons to provide aromatic character.
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Representative heteroaryl (heteroaromatic) groups are pyridinyl, pyrimidinyl,
pyrazinyl, pyridazinyl, furanyl, benzofuranyl, thienyl, benzothienyl,
thiazolyl,
thiadiazolyl, imidazolyl, pyrazolyl, triazolyl, tetrazolyl, isothiazolyl,
benzothiazolyl,
benzoxazolyl, oxazolyi, pyrrolyl, isoxazolyl, 1,3,5-triazinyl and indolyl
groups.
The heteroaryl group can be joined to the rest of the molecule through a bond
at
any substitutable carbon or nitrogen.
"PMB" means p-methoxybenzyl.
"Triflate" means trifluoromethanesulfonyl.
The term "derivative thereof' used in connection with a compound means
a structurally related compound which is obtainable by common chemical,
transformation of one or more functional groups existing or derivable from
groups existing on the original molecule.
The present invention is an improved process for preparing the CCR5
receptor antagonist compound of Formula I, preferably wherein R10 is CH3, and
is therefore the compound of Formula Id.
F
CH3
, ' .
N
N H3C N
o~\\ )
0 N N
o CH3 Formula I
In one embodiment, the present invention is an improved process for
preparing the intermediate compound of Formula A4,
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F ~
I /
' = 12HBr ]
N
NH
V v Formula A4
from which, in accordance with Scheme III, the compound of Formula I is
prepared.
Scheme III
Step 1
I ~ F
H CH
N 2 HBr
/~ N
S~ N ~NH '-'" Nr:D"'~ ~,NH
O O OO
A4 A4fb
Step 2
H3C N
N N
0 CH3 CH3
A4fb 2B G
E-G Al t.,,S~N~ N Hs N
N
00
)õ \ N
IX 0 CH3
Step 3
F o
CH,
Rt0-M R10
IX N (N H3 N
0
o'S.
~o ~
N
CH
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wherein R10-M is an organometallic reagent supplying R10, preferably the
organometallic reagent is methyl Grignard and R10 is methyl. The process of
Scheme III for preparing the compound of Formula I is described in published
intemational application No. WO 2006/074270 (herein, "the '270 publication"),
the
disclosure of which is incorporated herein by reference. Accordingly, Scheme
III
shows that the compound of Formula I is prepared by converting the compound
of Formula A4 into a free base form (shown in Scheme III as the compound of
Formula A4fb), by treating the compound with a base, for example, sodium
carbonate. Once obtained the free base compound A4fb is reacted with
piperidin-4-one compound 2B (step 2 of Scheme III) in the presence of a
reactant
having a facile leaving group (G) and an electrophilic group (E) capable of
scavenging the oxygen of the piperidin-4-one moiety during-the addition
reaction.
As described in the '270 publication, examples of compounds having such an E-
G structure include cyanating agents, for example, HCN, acetone cyanohydrin;
cyclohexanone cyanohydrin; a mixture of (C2H5)2AICN and Ti(OPr)4, a mixture of
acetic acid, H2SO4; NaHSO4, KHSO3 or Na2S2O5 and a cyanide source such as
NaCN or KCN; trimethylsilylcyanide; glycolonitrile; mandelonitrile;
glycinonitrile;
acetone amino nitrile; and dimethylaminoacetonitrile. Most preferably, the E-G
Ho CN
reagent is 2-hydroxy-2-methy{-propionitrile, (acetone cyanohydrin).
Without wishing to be bound by theory, it is believed that providing an E-G
compound to the reaction mixture promotes addition of the nitrogen group of
compound A4 to carbon 4 of the piperidine ring. It is further believed that
the E-
G reagent concomitantly supplies a facile leaving group substituent which, in
the
course of the reaction, is transferrred to carbon 4 of the piperidine ring.
Thus,
the E-G reagent provides a substituent to the intermediate compound of Formula
IX which is easily replaced in a subsequent step by an carbanionic R10 group
via
reaction of the intermediate of Formula IX with an organometallic ragent
supplying R10. Preferably the organometallic reagent is a methyl Grignard
reagent, supplying -CH3 forming the compound of Formula Id wherein R10 is
methyl.
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In one embodiment, the present invention provides compound A4 in
accordance with Scheme 1c, by reacting the compound of Formula A3 with 3-(S)-
methypiperazine-l-carboxylic acid benzyl ester, having a CBZ protecting group
on the nitrogen of ring position no. 1, replacing the benzotriazole moiety on
A3.
The product of this reaction is subsequently reacted in situ with a 3-fluoro-
benzyl-
Grignard reagent, for example, 3-fluoro-magnesium bromide, followed by
treatment of the reaction mixture with HBr to remove the CBZ protecting group
and precipitate the product (the compound of the Formula A4) as the HBr salt.
Scheme 1 c
F
N
HN
N N ~ / 0
1 Caz
OH F ~~ OH
~2. O 3. HBr '7"\\O 2HBr
A3 A4
The reaction shown in Scheme 1 c is preferably carried out in accordance
with published conditions, for example, those described in published
international
application no. WO 03/084942, which also describe preparation of 3-methyl-
piperazine-1 -CBZ. Preferred conditions for carrying out the reaction include
carrying out Step 1 of the reaction in refluxing toluene catalyzed by para-
toluenesulfonic acid, with azeotropic distillation to remove water. Step 2 is
preferentially carried out with the reaction mixture maintained at a
temperature of
from about 0 C to about 5 C. Phase 3 is preferentially carried out by addition
of
aqueous HBr to the reaction mixture, agitation for 10 minutes with subsequent
removal of the aqueous layer, followed bv heating for 3 hours to about 70 C.
Subsequent cooling and the addition of isopropanol is preferred to precipitate
the
HBrsaltofA4.
Accordingly, the method of the present invention provides compound A4
directly as the sulfonamide from an isolated benzotriazole adduct (the
compound
of Formula A3) without the need to provide a precursor having two different
protecting groups, which are removed sequentially to permit addition of the
21
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WO 2008/079284 PCT/US2007/026049
sulfonamide group to the desired nitrogen and leave the other nitrogen
available
for further reactions after the sulfonamide group is put in place.
As shown in Scheme 1 c, the no. 1 nitrogen of the piperazine moiety is
preferably protected by Cbz, (carbobenzyloxy moiety), an acid-labile nitrogen
protecting group. Other acid labile nitrogen protecting groups may
altematively
be used, for example, CZ3CO (where Z is a halogen), 2-trimethylsilylethyl
carbamate, 1-methyl-1-phenylethyl carbamate, t-butyl carbamate, cyclobutyl
carbamate, 1-methylcyclobutyl carbamate, adamantyl carbamate, vinyl
carbamate, allyl carbamate, cinnamyl carbamate, 8-quinolyl carbamate, 4,5-
diphenyl-3-oxazolin-2-one, benzyl carbamate, 9-arithrylmethyl carbamate,
diphenylmethyl carbamate, S-benzylcarbamate, methyl carbamate, ethyl
carbamate, diphenylphosphinyl, benzenesulfenyl, RCO (where R is C1_6alkyl),
benzoyl and other common acyl groups. Altematively, it will be appreciated
that
the N-1 nitrogen of the piperazine moiety can be protected with base-labile
protecting groups, for example, 9-fluorenylmethyl carbamate (FMOC), which are
later removed by treatment with a base rather than an acid. It will be
appreciated
that other protecting groups may alternatively be.used in the present process,
for
example, those described in Protecting Groups in Organic Synthesis, 3rd ed.,
T.
Green, W. Theodora, and P.G.M. Wuts, John Wiley & Sons, NY 1999, pp 504 to
615, which is incorporated herein by reference in its entirety. It will also
be
appreciated that deprotection of the nitrogen moiety initially protected by
the
protecting group can be carried out using other methods than treatment with
HBr,
for example, treating with other protic acids, for example HCI, HI, and H2SO4,
treating with Lewis acids, for example AIX3, and BX3, wherein "X" is a
halogen, as
well as by hydrogenation, for example, treatment. Of the compound with H2 in
the
presence of a hydrogenation catalyst, for example, palladium on carbon.
In one embodiment of the present invention, the compound of Formula A3
is provided by preparing an aldehyde intermediate (A2b) from the compound of
Formula Al in accordance with Scheme 1 b2. The compound of Formula Al is -
either oxidized or reduced, depending upon the "A" substituent present, to
provide the intermediate aldehyde (compound A2b) which is in turn reacted with
22
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WO 2008/079284 PCT/US2007/026049
benzotriazole to provide intermediate A3. Thus A3 is prepared in accordance
with Scheme 1 b2.
10 Scheme 1 b2
~
N
A 0 N-N OH
N ~
N Oxidizing or N N' ~ N
0=5=0 Cond'tions O-S~O H~ / 0=S=0
A A A
Al A2b A3'
wherein substituent "A" is selected from: (i) a substituent of the Formula -
C(O)-X,
wherein "X" is selected from: halogen; trialkylsilane; NR2R3, wherein R2 is
independently selected from hydrogen, an aliphatic moiety, an aromatic moiety,
and a heterocyclic moiety, and R3 is independently selected from hydrogen, 0-
R2, NR22, an aliphatic moiety, an aromatic moiety, and a heterocyclic moiety,
or
R2 and R3 taken together form a ring; and -S-R1 and -O-R', wherein R' is
selected from hydrogen, an aliphatic moiety, including an alkyl, alkyaryl, an
aromatic moiety, and a heterocyclic moiety; (ii) an alkyl-alkenyl=substituent
of the
formula -CHC(R20)2 wherein R20 is independently selected from H, alkyl and
aryl;
(iii) -CN; and (iv) -CH2OH. Preferably, the "A" substituent is selected from:
(i) a
substituent of the Formula -C(O)-X, wherein "X" is selected from halogen,
trialkylsilane, and -O-R', wherein R' is selected from hydrogen and an
aliphatic,
aromatic;.or heterocyclic moiety; (ii) a substituent of the Formula -
C(O)NR2R3,
23
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WO 2008/079284 PCT/US2007/026049
wherein R2 is independently selected from hydrogen, an aliphatic moiety, an
aromatic moiety, and a heterocyclic moiety, and R3 is independently selected
from hydrogen, O-R2, NR22, an aliphatic moiety, an aromatic moiety, and a
heterocyclic moiety; (iii) -CN; and (iv) -CH2OH,
For preparation of the intermediate aldehyde of Formula A2b, reducing
conditions are selected when the "A" substituent is -CN or contains a carbonyl
group bonded to the piperazine ring, for example, when "A" is C(O)-X.
Preferably, reducing reagents are selected from hydride reducing agents, for
example, diisobytyl aluminum hydride (DIBAL-H), sodium bis(2-
methoxyethoxy)aluminum hydride (RED-Al ), and lithium aluminum hydride.
When A" is an acid halide, reduction can be carried out using hydrogen in the
presence of a noble metal catalyst, for example Pd. When "A" is, for example,
an
alcohol, for example, CH2OH, In some embodiments, for example, when "A" in.
the compound of Formula Al is an alcohol, for example CH2-OH, it is preferred
to
use oxidizing conditions to prepare aidehyde intermediate. Examples of
oxidizing
conditions include treatment with enzymatic alcohol dehydrogenase, Dess-Martin
periodate, Swern Oxidation, Moffat Oxidation, inorganic catalyst mediated
oxidation, for example, oxidation using N-methylmorpholine oxide mediated by
RuC13, and organic catalyst mediated oxidation, for example oxidation with
sodium hypochlorite catalyzed by 2,2,6,6-tetramethyl-l-piperinyloxy (TEMPO).
In some embodiments wherein "A" is selected to be an -alkenyl moiety, it
is preferred to carry out oxidation with ozone followed by a suitable workup.
Examples of suitable workup include reductive workup using dimethylsulfide,
and
dihydroxylation followed by diol cleavage.
Well known literature procedures for oxidation or reduction of the types of
=substituents appearing on compound A2a to an aidehyde functional group are
found in: Acid to aldehyde: "Comprehensive Organic Synthesis" Eds. B. M. Trost
and I. Fleming, Pergamon, Oxford, (". 991), Vol 8, parts 1.11 and 1.12, pp
259=
306; Ester to aidehyde: Feldman, K. S. et al. J. Am. Chem. Soc. 1994 116, 9019-
9026; Thioester to aidehyde: Ho, P.T.; Ngy, K-y J. Org. Chem. 1993; 58, 2313-
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WO 2008/079284 PCT/US2007/026049
2316; Amide to aldehyde: Hagihara, M.; Schreiber, S. L. J. Am. Chem. Soc,
1992, 114, 6570-6571; Nitrile to aidehyde: Guilard, G. et al. J. Am. Chem. Soc
1992, 114, 9877-9889; Acyl silane to aldehyde: Cirillo, P. F.; Panek, J. J.
Tetrahderon Lett. 1991, 32, 457-460; Acid halide to aldehyde: Chen, C-y.et al.
J.
Org. Chem. 1994, 59, 3738-3741; Alcohol to aidehyde: Enzyme: Yamazaki, Y.;
Hosono, K. Tetrahderon Lett 1988, 29, 5769-5770; Alcohol to aldehyde:
Chemical: Leanna, M. R.; Sowin, T. J..; Morton, H. E. Tetrahderon Lett 1992,
33,
5029-5032; Alkene to aldehyde: Ozone: March J. Advanced Organic Chemistry:
Reactions, Mechanisms, and Structure, 4th Ed., John Wiley and Sons, New York,
1992, pp1177 and following; Dihydroxylation and diol cleavage: ibid at p822
and
following, p 1174 and following, all of which are incorporated by reference
herein
in their entirety.
In one embodiment of the present invention, it is preferred for the
compound of the structure of Al to be the sulfonamide amide compound A1 a(a
sulfonamide with a primary amide substituent on piperidine ring carbon no. 4),
it
is preferred to provide intermediate compound A3 in accordance with Scheme
1b1.
Scheme I b1
O NH2 N
CN N-N
OH
1. DIBALH
POCI 2. Aqueous Citric
N
6N I --~ I Acid workup
N
0=S=0 0=S=0
IQ c/j~\ 3 H`
~ ~ `
,N
~ O O
Ala A2a A3
wherein the primary amide substituent of A1 a is dehydrated by treatment with
POCI3 to the corresponding nitrile compound (A2a). Preferably, the dehydration
is carried out in an acetonitrile solvent. In this erribodiment, preferably
the nitrile
compound A2a is subsequently reduced to the corresponding aidehyde using
diisobutyl aluminum hydride in toluene with an aqueous citric acid workup.
This
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aldehyde intermediate is subsequently reacted, as described above, with
benzotriazole to yield intermediate compound A3. It will be appreciated that
conversion of the amide group of the compound of Formula A1 a to a nitrile
group
can also be carried out using other dehydrating agents, for example, thionyl
chloride, phosgene, phosphorous pentoxide, and oxalyl chloride. In some
embodiments using alternative dehydrating agents to perform this
transformation,
known conditions are employed, for example, those described in Comprehensive
Organic transformations, 2nd ed., R.C. Larock, Wiley-VCH, NY 1999, on pages
1983 to 1985, which are incorporated herein by reference.
In one embodiment of Scheme 1 b1, the reaction is preferably carried out
by charging a toluene solution of DIBAL-H to a solution of A1 a in
tetrahydrofuran,
(THF) at a temperature between -15 C and 0 C. Following addition of DIBAL-
H, the reaction mixture is agitated for about two hours with the temperature
of the
reaction mixture maintained at about 20 C. The reaction mixture is quenched
with a solution of aqueous citric acid, generally by stirring the reaction
mixture
with the solution, for example, for a period of one hour. The organic
(toluene/THF) and aqueous layers of the mixture are then separated, and the
toluene(fHF solution of compound A2a is retained for subsequent treatment with
benzotriazole. The third step is carried out by adding a THF solution of
benzotriazole the solution of aldehyde compound A2a provided by the DIBAL-H
reduction. The THF is distilled off and the reaction mixture is refluxed
(refluxing
temperature approximately 110 C). After completing the reaction, the reaction
mixture is cooled to a temperature of from about 20 C to about 30 C, during
which benzotriazole adduct A3 precipitates out of solution. Adduct A3 is then
filtered, washed with toluene, and dried.
Optionally, the intermediate A2a aldehyde compound can be isolated by
removal of the solvent before forming benzotriazole adduct A3, yielding a
waxy,
low melting solid. The A2a compound is then stored and handled under an inert
atmosphere until it is used to prepare the benzotriazole adduct to prevent
oxidation.
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In some embodiments of the present invention the intermediate
compound of Formula A3 is a compound of Formula A3', and it is preferred to
prepare the intermediate compound of Formula A3' in accordance with Scheme
I IB,
Scheme IIB
Step 1
0 CI ~/ so2a 0
NHZ TEA ci NH2
NH N
s :)
o
2Ba 0 2Bb
Step 2
CI
POC13 N CN
2Bb g
H3C-CN 11 4k- O
0 2Bc
Step 3
CN
Potassium t-butoxide/ 0
N
2Bc THF ~S~
17- 0
A2a
Step4
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WO 2008/079284 PCT/US2007/026049
CN
1. DIBALH N N I
2. Aqueous Citric N
Acid workup
N 3. H.
I S N
0=5=0 N-N O OH
11 ~`O A3~
N
A2a
Accordingly,synthesis scheme IIB comprises:
(i) reacting isonipecotamide (compound 2Ba) with 3-chloropropane-sulfonyl
chloride to form the adduct compound 2Bb;
(ii) converting the amide substituent of compound 2Bb to a nitrile
substituent,
thereby forming compound 2Bc;
(iii) cyclizing the 3-chloropropyl substituent on the sulfonamide substituent
of
compound 2Bc to form compound A2a; and
(iv) reacting compound A2a with benzotriazole to form benzotriazole adduct
compound A3'.
Alternatively, starting with compound 2Bb, steps 2 and 3 can be reversed,
treating the compound of Formula 2Bb with a metal alkoxide to cyclize the
chloropropyl substituent on the sulfonamide moiety, yielding the
cyclopropylsulfonamide amide compound of Formula 2Bd,
O
D- S = Nl:l4
ONH2
~ 2Bd
and then treating the compound of Formula 2Bd with phosphorous trichloride to
convert the amide functional group to a nitrile, providing the compound of
Formula A2a. The conversion of the amide group in the compound of Formula
2Bd can alternatively be accomplished with other dehydrating agents, for
example, but not limited to, thionyl chloride, phosgene, phosphorous
pentoxide,
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WO 2008/079284 PCT/US2007/026049
and oxalyl chloride. In some embodiments using alternative dehydrating agents
to perform this transformation, known conditions are employed, for example,
those described in Comprehensive Organic transformations, 2"d ed., R.C.
Larock,
Wiley-VCH, NY 1999, on pages 1983 to 1985, which are incorporated herein by
reference.
Variations on Scheme IIB can also include utilizing differently functional
piperidine compounds in place of 2.Ba for use in either the altemative or non-
altemative Scheme IIB processes. Thus, for example, compound 2Ba-1 can be
prepared according to Scheme IIB-1:
I I B-1
0
NH2
HN HN
2Ba 2Ba-1
by converting the primary amide functional group to a nitriie in accordance
with
the above-described processes or those described in Comprehensive Organic
Transformations, 2"d ed., Richard Larock, Wiley-VCH, NY 1999, pp 1983 to 1985,
which is incorporated herein by reference. When used in Scheme IIB, Step 1, in
place of 2Ba, it provides the compound of Formula 2Bc directly. When used in
the alternative embodiment of Scheme IIB, it provides the compound of Formula
A2a directly in Step 1. When used as compound A1c in the Scheme of Formula
IIA (below) it provides the cyclypropylsulfonamidenitrile compound of Formula
A2a directly also.
By providing a method of cyclizing the cyclopropyl ring after forming the
sulfonamide compound of Formula 2Bb (as shown in Scheme IIB), the need to
prepare cyclopropyisulfonyl chloride is obviated. In carrying out Scheme IIB
it is
preferred to employ acetonitrii'e as a solvent and triethylamine (TEA) as a
base
which catalyzes the sulfonamide formation in Step (i). In some embodiments
utilizing Scheme 1IB, it is preferred to perform Step (ii), conversion of the
amide
substituent to a nitrile substituent by treating compound 2Bb with phosphorous
oxychloride in acetonitriie. In some embodiments utilizing Scheme Ilb, it is
preferred to carry out cyclopropanation Step (iii) by treating compound 2Bc
with
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WO 2008/079284 PCT/US2007/026049
potassium tert-butoxide in tetrahydrofuran (THF) solvent. It will be
appreciated
that other known base compounds having similar or greater proton affinity can
be
employed to cyclize the chloropropyl moiety present in either the compound of
Formula 2Bb or in the compound of Formula 2Bc.
As discussed above, in some embodiments of the present invention the
intermediate compound of Formula A3 is altematively prepared from the
sulfonamide compound of Formula Al, wherein the substituent "A" is selected
from: (i) a substituent of the Formula -C(O)-X, wherein "X" is selected from:
halogen; trialkylsilane; NR2R3, wherein R2 is independently selected from
hydrogen, an aliphatic moiety, an aromatic moiety, and a heterocyclic moiety,
and
R3 is independently selected from hydrogen, O-R2, NR22, an aliphatic moiety,
an
aromatic moiety, and a heterocyclic moiety, or R2 and R3 taken together form a
ring; and -S-R1 and -O-R', wherein R' is selected from hydrogen, an aliphatic
moiety, including an alkyl, alkyaryl, an aromatic moiety, and a heterocyclic
moiety; (ii) an alkyl-alkenyl-substituent of the formula -CHC(R20)2 wherein
R20 is
independently selected from H, alkyl and aryl; (iii) -CN; and (iv) -CH2OH,
where
the compound of Formula Al is prepared in accordance with synthesis Scheme
IIA.
Scheme IIA
S
0
'4 V \O A
HN 0 S/N
Alc ~ Np Al
Where substituent "A" is -CH2OH, -CONH2, -C(O)OEt, and -C(O)OH, the
compound Al c is a commercially available material. It will be appreciated
that
the remaining of the above listed substituents can be prepared from one or
more
of these commercially available materials. Preparation of cyclopropanesulfonyl
chloride is known, for example, the procedure described in Organic Sulfur
Mechanisms. 36. Cyclopropanesulfonyl chloride: its mechanisms of hydrolysis
CA 02673233 2009-06-18
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and reactions with tertiary amines in organic media, King, James F.; Lam, Joe
Y.
L.; Ferrazzi, Gabriele. Dep. Chem., Univ. West. Ontario, London, ON, Can.
Joumal of Organic Chemistry (1993), 58(5), 1128-35.
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EXAMPLES
The following solvents and reagents may be referred to by their
abbreviations in parenthesis:
sodium bis(trimethylsilyl)amide : NaHMDS
triethyl amine: TEA
trifluoro acetic acid: TFA
tertiary-butoxycarbonyl: t-BOC
tetrahydrofuran: THF
lithium bis(trimethylsilyl)amide: LiHMDS
Methyl tert-butyl ether: MTBE
DIBAL-H: Diisobutyl Aluminum Hydride
Dimethyl Sulfoxide d6: DMSO
Deuterated chloroform: CDCI3
Deuterium oxide: D20
mole: mol.
millimole: mmol
Hertz: Hz
Chemical Shift (NMR): S
singlet = s
doublet = d
triplet = t
broad = b
Melting Point = MP
Example 1: Preparation of sulfonamide-amide A1a
0 CI S02CI O
NH2 TEA NH2
NH
7iIo
~2Ba
O Ala
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With reference to Scheme IIB, above, wherein Path B is followed in Step
2, compound 2Ba (isonipectoamide, article of commerce, used as received)
(36.5 g, 285 mmol), acetonitrile (150 mL), and saturated aqueous potassium
carbonate solution (150 mL) were added to a 1 liter jacketed vessel. To this
mixture was charged 3-chtoropropane sulfonyl chloride (40.0 g, 285 mmol),
keeping the temperature between 15 C and 25 C. The reaction was then
stirred for about 15 minutes. MTBE (500 mL) was then charged, and the
resulting precipitated product A1 a was filtered, and washed with MTBE (3 x
100
mL). The solids were dried under vacuum oven at 20 to 30 C to yield 51.2 g
(77.3%) of product Ala as a white solid.
'H NMR (DMSO, 400 MHz): S 7.31 (1 H, s), 6.86 (1 H, s), 3.58 (2H, ddd, J =
12.0,
3.2, 3.2 Hz), 2.81 (2H, ddd, J= 12.0, 12.0, 2.4 Hz), 2.57 (1 H, m), 2.21 (1 H,
dddd,
J= 10.8, 10.8, 3.2, 3.2 Hz), 1.79 (2H, dddd, J= 13.2, 2.8, 2.8, 2.8 Hz), 1.53
(2H,
dddd, J = 13.6, 13.6, 13.6, 4.0 Hz), 0.99 - 0.88 (4H, m). MP: 151 C
Example 2: Preparation of sulfonamide-nitrile A2a from Ala
CN
Ala POC13 S 1-0 N
H3C-CN 11 4"'0
O A2a
Compound A1 a(50.0g, 215 mmol) and acetonitrile (200 mL) were
charged to a 1 liter jacketed flask and were heated to 55 to 60 C.
Phosphorous
oxychloride (POCI3, 50.1 g, 323 mmol) was added, keeping the temperature at
about 60 C. The reaction was kept at 60 C for about 6 hours, at which time
toluene (250 mL) was added. The reaction was allowed to cool to 25 C and
was slowly quenched with saturated aqueous potassium bicarbonate (350 mL),
keeping the temperature below 30 C. The layers-.were separated, and the
aqueous layer was extracted with toluene (200 mL). The organic layers were
combined, washed with brine (75 mL) and dried over anhydrous magnesium
sulfate. The organic layer was then filtered, and the solvent was removed
under
reduced pressure to yield 42.1 g (91.3%) of compound A2a as an off-white
solid.
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WO 2008/079284 PCT/US2007/026049
'H NMR (CDCI3, 400 MHz): S 3.44 - 3.42 (4H, m), 2.89 (1 H, tt, J = 6.0, 4.8
Hz),
2.27 (1 H, tt, J = 8.0, 4.8 Hz), 2.05 - 1.97 (4H, m), 1.19 (2H, m), 1.03 (2H,
m).
MP: 91.9 C.
Example 3: Preparation of open-chain sulfonamide-amide 2Bb
O CI SO2CI 0
NH2 TEA NH2
CI S/
N
00
NH
~1 ""0
2Ba 0 2Bb
With reference to Scheme IIB (primary Scheme), Step 1, compound 2Ba
(isonipectoamide) (54.7 g, 424 mmol) acetonitrile (750 mL), and triethylamine
(47.2 g, 466 mmol) were charged to a 2 liter jacketed flask and agitated at
about
C. The flask was charged 3-chloropropanesulfonyl chloride (75.0 g, 424
mmol) dissolved in acetonitrile (120 mL) through an addition funnel over one
hour, keeping the temperature of the reaction mixture at about 20 C, and
stirred
15 for four to five hours after addition. To the agitating reaction mixture
were added
10% aqueous citric acid (500 mL) and ethyl acetate (500 mL). The layers were
allowed to split, and the bottom, aqueous layer was extracted with ethyl
acetate
(300 mL). The organic layers were combined and washed with 10% aqueous
citric acid (400 mL) and brine (200 mL). The batch was concentrated under
20 reduced pressure, and the resulting solids were washed with MTBE to yield
53.0
g (46.5 %)compound 2Bb as an off-white solid.
' H NMR (DMSO, 400 MHz): S 7.32 (1 H, s), 6.86 (1 H, s), 3.74 (2H, dd, J =
6.4,
6.4 Hz), 3.58 (2H, m), 3.14 (2H, m), 2.80 (2H, ddd, J = 12.0, 12.0, 2.4 Hz),
2.20
(1 H, dddd, J = 11.4, 11.4, 3.8, 3.8 Hz), 2.09 (2H, m), 1.78 (2H, m), 1.51
(2H, m).
MP: 171 C
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Example 4: Preparation of open-chain sulfonamide-nitrile 2Bc
CN
Ci
2Bb POC13 CSN
H3C-CN 11 O
0 2Bc
With reference to Scheme IIB (non-altemative method) compound 2Bb
preapared in Example 3 (5.0 g, 18.6 mmol), acetonitrile (20 mL), and
phosphorous oxychloride (4.28 g, 27.9 mmol) were charged to a 100 mL flask,
and heated to 60 C. The reaction was kept at 60 C for about four hours, and
then cooled to 20 to 25 C. The reaction was quenched by the slow addition of
10% aqueous sodium citrate. After quenching, the pH of the reaction was
adjusted to 4-5 by the addition of 4 M sodium hydroxide solution. The
resulting
mixture was extracted with ethyl acetate (2 x 75 mL), and the combined organic
layers were washed with water (25 mL) and brine (25 mL). The solvent was then
removed under reduced pressure to yield 4.09 g (87.7%) compound 2Bb as an
off-white solid.
'H NMR (DMSO, 400 MHz): S 3.73 (2H, dd, J = 6.4, 6.4 Hz), 3.34 (2H, m), 3.20 -
3.01 (5H, m), 2.10 (2H, m), 1.94 (2H, m), 1.76 (2H, m). MP = 78.8 C
Example 5: Preparation of sulfonamide-nitrile A2a from 2Bc
CN
Potassium t-butoxide/ O N
2Bc THF ~g~
V` `O
A2a
With reference to Step 3 of Scheme IIB (above) potassium tert-butoxide
(2.19 g, 17.9 mmol) was dissolved in THF (30mL) and cooled to -15 C.
Compound 2Bc was separately dissolved in tetrahydrofuran (20 mL) and
charged to an addition funnel. Compound 2Bc in tetrahydrofuran was then
added to the solution of potassium tert-butoxide over about 10 minutes,
keeping
CA 02673233 2009-06-18
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the temperature below 0 C. The reaction was allowed to stir at -15 C for
about
1 to 2 hours, and was quenched with 10% aqueous citric acid (50 mL). The
mixture was extracted with ethyl acetate (60 mL), and the organic layer was
washed with water (10 mL), and brine (10 mL). The solvent was removed under
reduced pressure to yield crude compound A2a, which was then washed with
MTBE (3 x 15 mL) to yield 2.01 g (78.2%) of compound A2a. The'H spectrum
was identical to that of compound A2a formed in example 2.
Example 6: Preparation of compound A3 from A2a
1. DIBAIH q N
~~
~ 2. Aqueous Citric ~ N~ N
>cN -S-N Acid workup S-N
O
3. H OH
AZa % N-N A3
6
With reference to Scheme 1 B1, above, Compound A2a (107 g, 500 mmol)
and tetrahydrofuran (640 mL) were charged to a 3 liter jacketed flask
and'stirred
at 20 C until solids had all dissolved. The reaction was then cooled to about
-
10 C. Diisobutyl aluminum hydride (DiBAL-H, 400 mL of a.1.5 M solution in
toluene, 600 mmol) was then added, keeping the reaction mixture between -15
C and 0 C. The reaction was stirred at this temperature range for 2 hours
after
addition of DiBAL-H, and was then quenched into a 25% aqueous solution of
citric acid (500 mL), keeping the temperature of the quench below 40 C. The
quenched batch was allowed to stir for 1 hour at 20 C, and was then settled
and
split. The lower, aqueous layer was extracted with toluene (600 mL), the
organic
layers were pooled, and washed with water (200 mL).-
In a separate vessel, benzotriazole (59.6 g, 500 mmol)-was dissolved in
tetrahydrofuran (500 mL). The benzotriazole solution was then charged to the
batch, and the batch was heated to reflux. The batch was then distilled under
atmospheric pressure to about 1.1 L (10 X volume with respect to A2a) and
cooled to about 60 C. Toluene (500 mL) was then added, and the batch was
redistilled under atmospheric pressure to 1.1 L. The batch was then cooled to
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WO 2008/079284 PCT/US2007/026049
20 - 30 C, at which time solid A3 crystallized out. Toluene (500 mL) was then
added and the batch was filtered, washed with toluene (500 mL), and dried
under vacuum to yield 145 g (86.4%) compound A3 as a white solid.
'H NMR (DMSO, 400 MHz. n.b. Compound A3 slowly decomposes back to its
parent aidehyde and benzotriazole over time when stored in DMSO solution):
S 8.06 (1 H, d, J = 8.8 Hz), 7.96 (1 H, d, J = 8.4 Hz), 7.51 (1 H, ddd, J =
8.0, 8.0,
0.8 Hz), 7.45 - 7.40 (2H, m), 6.08 (1 H, dd, J = 9.2, 6.4 Hz), 3.70 (1 H, bd,
J =
12.0 Hz), 3.48 (1 H, bd, J= 12.0 Hz), 2.87 (1 H, ddd, J= 12.8, 12.8, 2.4 Hz),
2.68
(1 H, ddd, J= 12.0, 12.0, 2.4 Hz),.2.56 - 2.49 (2H, m), 2.43 (1 H, ddddd, J=
8.4,
8.4, 8.4, 3.6, 3.6 Hz), 2.14 (1 H, bd, J= 12.4 Hz), 1.50 (1 H, dddd, J= 12.4,
12.4,
0
12.4, 4.4 Hz), 1.25, (1 H, dddd, J= 12.4, 12.4, 12.4, 4.0 Hz), 098 = 0.85 (5H,
m).
MP: 139 C.
Example 7: Preparation of compound A4 from A3
Y XOH HN F (
CBZ /
1. _
N F MgBr N
2. \ N
0=S=0 \ NH
3. HBr \O 2HBr
A3 A4
With reference to Scheme 1 c, above, compound A3 prepared in Example
6 (20.0 g, 59.5 mmnol), 3-(S)-methyl piperazine-1-carboxylic acid benzyl ester
(14.6 g, 62.9 mmol), p-toluenesulfonic acid (0.12g) and toluene (240 ml) were
placed into a 1 L, three-necked flask equipped with a Dean-Stark water trap, a
mechanical stirrer and a thermometer. The mixture was heated at reflux for 18
hours. The mixture was then distilled to reduce the volume to 10X (200 mL).
The mixture was cooled to 0 C -5 C and to this was added a solution of 3-
fluorophenyl magnesium bromide (1 M in THF, 64 mi). A solution of sodium
citrate in water (17.6 g/80 ml) was then added to the mixture and stirred for
2
hours. The reaction mixture was settled and split to remove the lower aqueous
layer. The organic layer was washed with water (80 mL). The organic solution
37
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WO 2008/079284 PCT/US2007/026049
was extracted with aqueous HBr (48% aqueous, 60 ml). The aqueous HBr
solution was agitated at 80 C -90 C for 4 hours. The mixture was cooled to
40 C and to this was added isopropyl alcohol (300 mL). The mixture was held
at 40 C for 2 hours then cooled to 5 C and held at 5 C for 18 hours to
complete the crystallization. The product was filtered and washed with
isopropyl
alcohol (200 ml). The wet cake was dried in a vacuum oven at 55 C for 18
hours to give 21.2 g (74.8%) compound A4 as a white solid.
'H NMR (D20, 400 MHz): & 7.39 (1 H, dd, J-14.4, 8.0 Hz), 7.22 - 7.12 (3H, m),
4.74 - 4.60 (2H, overlap with HOD peak), 4.49 (1 H, d, J = 10.0 Hz), 3.79 (1
H,
bd, J= 12.6 Hz), 3.63 (1 H, bd, J= 12.0 Hz), 3.55 (1 H, bd, J= 12.8 Hz), 3.44 -
3.29 (4H, m), 3.21 (1 H, dd, J = 12.2, 12.2 Hz), 3.10 (1 H, bs), 2.84 (1 H,
dd, J =
12.0,12.0 Hz), 2.70 (1 H, dd, J= 12.0, 12.0 Hz), 2.40 - 2.36 (2H, m), 1.93 (1
H,
bd, J= 12.6 Hz), 1.40 - 1.29 (1 H, m), 1.36 (3H, d, J= 6.0 Hz), 1.14 - 1.06
(2H,
m), 0.98 - 0.90 (4H, m). MP: 200 C.
The above description of the invention is intended to be illustrative and
not limiting. Various changes or modifications in the embodiments described
herein may occur to those skilled in the art. These changes can be made
without departing from the scope or spirit of the invention
38
